Five attack submarines could be decertified this year if Congress fails to provide more money to the Navy to address maintenance and readiness shortfalls, according to government officials.

The Navy did not immediately respond to a request for comment on which submarines are at risk of decertification.

The SUBSAFE certification program, developed in response to the loss of the USS Thresher in 1963, requires that audits be performed at the end of major depot maintenance periods to maintain certification, similar to the way states require cars to pass certified inspections.

When a submarine fails to get the certification, it is not taken out of service entirely but is restricted in what kinds of duties it can perform.

Top officials with the Navy, Army, Air Force and Marine Corps said that budget constraints and uncertainty have forced them to make tough choices between addressing immediate operational needs and ensuring long-term readiness.

The officials were making the case for Congress to pass a supplemental defense spending bill at a House Armed Services Committee hearing on the "state of the military" earlier this week.

"If we do not see some kind of supplemental come for this fiscal year ... within a month we're going to have to shut down air wings. We're going to have to defer maintenance on several availabilities for surface ships and submarine maintenance facilities. We would be just flat out of money to be able to do that," Vice Chief of Naval Operations Adm. Bill Moran said at the hearing.

Estimates for the additional funding are as high as $50 billion, according to U.S. Rep. Joe Courtney, D-2nd District, a member of the House Armed Services Committee. But, Courtney said, it's hard to say for sure what the number might be, and how the funding would be distributed to the various services.

"The administration and Pentagon will get the first crack, then it will come over to us," Courtney said referring to the Seapower and Projection Forces Subcommittee, which has oversight over the military's air and sea programs and is where vital discussions about funding for shipbuilding occur. Courtney retained his seat as ranking member of the committee.

The government currently is operating on a stopgap funding measure known as a continuing resolution until April 28. Even if Congress passes a budget to cover the second half of the fiscal year, budget caps put in place under the Budget Control Act of 2011 mean the Navy would receive about $5 billion less than it did last fiscal year. Combine that with the increase in spending by the Navy at the start of the year, and the Navy will run out of money for ship and submarine maintenance unless additional funding is approved by Congress.

"We've had cases in the recent past where we've had to decertify a submarine from being able to dive because we cannot get it into the nuclear maintenance that is needed," Moran said.

Ryan Alexander, president of the nonpartisan budget watchdog Taxpayers for Common Sense, said any additional funding should be provided through the normal appropriations process.

"Of course we should be concerned about readiness. There are real needs for military spending. But to go through the emergency appropriations process to address readiness is putting the cart before the horse," Alexander said.

While she acknowledged "we are living in an era of restrained spending," Alexander said if Congress wants to lift caps put in place under the Budget Control Act, it can do that through the normal legislative process. Spending needs to be based on available resources, priorities and strategy, she added.

While the Navy, following sequestration and furloughs in 2013, has hired back its civilian workforce in fairly substantial numbers, "they're young, they're inexperienced," Moran said.

"Today in our public shipyards, roughly 50 percent of all of our civilian workforce there has less than five years' experience," he added.

He also pointed to maintenance backlogs at public shipyards. The backlog has resulted in more maintenance and repair work being shifted to private shipyards like Electric Boat, which currently is working on the largest and most complex maintenance and modernization in the company's history with the overhaul of the USS Montpelier (SSN 765).

An average of 700 employees are assigned to the Montpelier, with surges of up to 900 people, according to EB spokesman Dan Barrett. Work is scheduled for completion in February 2018, Barrett said.

Courtney sees more opportunity for this type of work at EB in the future. And he said he remains confident that the Navy can continue its uptick in shipbuilding while simultaneously addressing maintenance shortfalls.